Ferrocene containing monomers and copolymers

ABSTRACT

The ferrocene-containing polymerizable monomers, pentaerythritol methacrylate tris (ferrocenoate) and pentaerythritol acrylate tris (ferrocenoate), are disclosed along with the pertinent preparative procedures therefor. The specified ferrocenecontaining monomers when copolymerized with butadiene serve as the propellant binder and catalyst for fast-burning composite propellants. The copolymers perform the functions of binder and catalyst in a propellant composition containing ammonium perchlorate, a plasticizer, and aluminum metal fuel.

United States Patent 1191 Stevens et al.

[11 3,857,870 [451 Dec. 31, 1974 FERROCENE CONTAINING MONOMERS' AND COPOLYMERS [76] Inventors: Travis E. Stevens, 1510 Montdale Rd., S.E.', Huntsville, Ala. 35801; Samuel F. Reed, Jr., 4009 Medford Dr., S.E., Huntsville, Ala. 35802 [22] Filed: July 31, 1969 [21] Appl. No.: 849,254

OTHER PUBLICATIONS Levi, Ferrocene Polymers: 'An Annotated Bibliography, 'Plastics Technical Evaluation Center, Picatinny Arsenal, Dover, N..l., 1966, p. 1, TPl l4ou6.

Primary ExaminerLeland A. Sebastian Attorney, Agent, or Firm- -Edward .1. Kelly; Herbert Berl; Jack W. Voigt [5 7] ABSTRACT -The ferrocene-containing polymerizable monomers,

pentaerythritol methacrylate tris (ferrocenoate') and pentaerythritol acrylate tris (ferrocenoate), are disclosed along with the pertinent preparative procedures therefor. The specified ferrocene-containing monomers when copolymerized with butadiene serve as the propellant binder and catalyst for fastburning composite propellants. The copolymers perform the functions of binder and catalyst in a propellant composition containing ammonium perchlorate, a plasticizer, and aluminum metal fuel.

5 Claims, No Drawings 4 1 CONTAINING 'MONOMER'S AND COPOLYMERS FERROCENE tial esterification ofpentaerythritol are known. Two

derivatives of pentaerythritol which serve as the starting compounds for. the preparation of the ferrocene containing monomers of this invention are pentaerythritol arsenite methacrylate and pentaerythritol arsenite acrylate.

The term polymerizable monomer is well known. The term when applied to the propellant art generally means a compound useful in propellants because. it is capable of forming an elastic tough rubbery polymer by condensation or polymerization reactions in the propellant mix. The resulting rubbery polymer functions as a binder forthe propellant charge. The binderprovides strength for the propellant charge or grain. Many of the prior art compounds have been concerned with binder materials. The present trend has been to increase the performance of propellants by employing an energetic binder material, improved oxidizer, and'burning rate catalyst. I

The prior art esters of polymerizable compounds have been employed as energetic binder materials having oxidizing and plasticizing capabilities. The term enprocess is 'a complex process requiring a proper bal-' ance of fuel, oxidizer, and catalysts. The'oxygen'content of a number of energetic binders of the prior art enables those binders to contribute to the oxidizing capability of the propellant composition in addition to the binder and catalyst which does not evaporate during propellant processing or migrate in the finished propellant.. I

SUMMARY OF THE INVENTION The ferrocene-containing monomers, pentaerythritol methacrylate tris (ferrocenoate) and pentaerythritol acrylate tris (ferrocenoate) are produced from pentaerythritol arsenite methacrylate and pentaerythritol arsenite acrylate respectively as the starting compounds.

The "monomers become constituents of copolymers of DESCRIPTION OF THE PREFERRED EMBODIMENTS The starting compound, pentaerythritol arsenitemethacrylate, formsone ofthe monomers of this invention and may be produceda's follows.

To a clear solution of 10.4 grams (0.050 mole) of. pentaeryth'ritol arsenite in 20 milliliters of acetonitrile.

and 8 milliliters of triethylamine is added drop wise a mixture of'5.5g.(0.05 2 mole)ofmethacryloyl chloride 1 v and 5 ml. of acetonitrile. The addition requires about 15 minutes while thetemperature is maintained at about 35C to about 40C by external cooling. The mix ture is stirred at 50C for 2 hours, then the solvent is rebinding cap'abilty of the'prop'ellant composition. ,Each I active ingredient in a propellant composition contributes to oneor more functions of the propellant system.

'Naturally, a multi-functionalingredient offers distinct advantages.

Generally, a burning rateadditive' has been required for use in the prior art propellant compositions to obtainincreased burning rates. These additives or catalysts have included metallic oxides and organo-metallic compounds. .Ferrocene and n-butyl ferrocene have been utilized as burning rate catalysts. The liquid ferrocene compounds have been effective in promoting The present invention has as its principal object to provide ferrocene-containing monomers which can be polymerized to form an energetic binder having a burning rate catalyst as an integral part thereof.

Another object is to provide copolymerization prodnets of ferrocene containing monomers and butadiene which serves as energetic binder and burning rate catalyst for propellant compositions.

A'further object of this invention is to provide a propellant composition having a combination energetic moved at reduced pressure, and the residue is dried at ambient temperature and l millimeter of pressure for 3-0 minutes. The residue-is extracted with three 100 ml. portions of hot ligroin (each containing 5 mg. of hydroquinone). The extracts are concentrated and chilled and the product removed by filtration. The solid obtained is recrystallized from ligroin to g'ive 5.40 grams of the monomer, pertaerythritol arsenite methacrylate, m.p. 83C to 845C.

Another starting compound pentaerythritol arsenite acrylate, forms anothermonomer-and may be produced as follows.

To a mixture of 10.4g. (0.050 mole) of pentaerythritol arsenite and 10 ml. ofacetonitrile is added 4.5 ml.

(0.065 mole) of acrylic acid followed by 24 ml. (0.175

mole) of triethylamine.- When the exotherm from't-he ,addition of the amine (the reaction temperature should not be allowed to exceed 20C) is subsided, 7.7 ml.

(0.060 mole) of. benzene-sulfonyl chloride in 10 ml. of

acetonitrile is added over a 15 minute period. The reaction mixture is cooled to keep the temperature below 30C during the addition; after the benzenesulfonyl chloride addition, the mixture is stirred'at30C for l hour, .The solvent is then removed at reduced pressure and the residue dried at ambient temperature and 'l millimeter of pressure for 30 minutes. The residue is extracted three times with 200 ml. of'hot ligroin con- Pentaerythritol methacrylate tris (ferrocenoate) .and pentaerythritol acrylate'tris (ferrocenoate) are monomers which are prepared as set forth hereinbelow under Example 1 and 11. The specified monomers when copolymerized with butadiene form binders that provide in addition to the binder function the function of catalysis for the propellant system wherein used. Example 111 and Example IV are illustrative of the procedures for preparation of the copolymers of this invention. Table 1 sets forth burning rates of uncured composite propellants using the hydroxy-terminated copolymer of butadiene and pentaerythritol methacrylate tris (ferrocenoate) as compared with a propellant using unmodified hydroxy-terminated polybutadiene, and a propellant using n-butyl ferrocene, a standard burningrate-promoter. Similarly, the copolymer of pentaerythritol acrylate tris (ferrocenoate) and butadiene may be used as the binder and catalyst for a propellant composition. I

EXAMPLE I Preparation of Pentaerythritrol Methacrylate Tris (ferrocenoate) A 2.20 g. (8 mole) sample of pentaerythritol arsenite methacrylate and mg. of dicyanobenzoquinoneis stirred with ml of acetone and 6 ml of water for minutes at C. The solution is filtered, and the filtrate is stripped to dryness. The residue, in methylene chloride, is dried over calcium sulfate. The solution is again stripped to dryness, and the residue taken up in 8 ml methylene chloride and 8 ml of chlorobenzene. This methacrylate tris (ferrocenoate), 1.14g, m.p. 109-1 12C.

um Analysis W Calculated for C H Fe O C. 60.0; H. 4.80; Fe. 19.94.

Found: C. 59.7; H. 4.80; Fe. 20.9

EXAMPLE 11 Preparation of Pentaerythritol Acrylate tris (ferrocenoate) 1 The procedure outlined in Example 1 above is followed using 1.71 g of pentaerythritol monoacrylate (prepared by hydrolysis of pentaerythritol arsenite acrylate) and 10 g. of ferrocenoyl chloride. The organic residue obtained upon evaporation of the organic solvents is re-crystallized from methanol. The yield is pens ljst i qttfi-(tetressaeetelt 1. .255 F I-P- l07-109C.

Analysis Calculated for C H Fe O C. 59.60; H. 4.64; Fe. 20.3.

Found: C. 59.1: H. 4.59; Fe. 19.7.

EXAMPLE 111 Copolymerization With Butadiene Introduce to a glass-high-pressure reactor (Aerosol tube): 30 ml. of toluene. 2.1 12g (0.0084 mole) azo-bis- (2-methyl-5-hydroxy-valeronitrile) as initiator. and 2.1g (0.0025 mole) pentaerythritol methacrylate tris- (ferrocenoate). The reactor is attached to a vacuum line and deaerated by three alternate freeze-thaw cycles. Butadiene (10.8g.. 0.2 mole) is condensed into the reactor, and the reactor transferred to an oil bath at 6667C. Heating is continued for a period of 72 hours. On cooling the-solvent is removed by evaporation and the copolymer reprecipitated by dissolving in ether followed by the addition of methanol. After'decanting the solvents, the copolymer is stripped of excess solvents on arotatory evaporator and finally dried at 70-75C. under reduced pressure (1 mm) for a period of 24 hours. The yield of liquid copolymer is 7.1

'g The copolymer is characterized by molecular weight (3,500), OH end groups (1.21 wt%) and elemental analysis (Fe. Found: 3.9).

EXAMPLE IV In a similar reaction to that set forth in Example 111, 5.4 g. (0.1) butadiene is copolymerized with 2.1g (0.0025 mole) of pentaerythritol methacrylate tris- (ferrocenoate) in toluene with 0.756 g. (0.003 mole) azo-bis-(Z-rncthyl-5-hydroxy-valcronitrile) as initiator to give 4.2 g. (56%) of the copolymer analyzing as follows: molecular weight (4,700). OH end groups (0.8 weight%) and elemental analysis (Fe. Found 6.9%).

As noted in Examples 111 and IV the mole ratio of butadiene to monomer is from about 40 to 1 to about 80 to 1 for the monomer selected. The mole ratio in Examples Ill and 1V is also satisfactory when the monomer pentaerythritol acrylate tris (ferrocenoate) is selected for copolymer preparation.

Burning Rate Data The hydroxy-terminated copolymer of butadiene and pentaerythritol methacrylate tris-(ferrocenate) containing 3.9% Fe. (prepolymer A of Table 1). providescenoate) may be used in place of the prepolymer, I butadieneand pentaerythritol methacrylate tris (ferrocenoate).

Table 1 Burning Rates of Uneured Composite Propellants Prepolymcr /1 Plaslici zcr "/1 NH ,ClOf/r A17: Additive "/1 R at R,, at

' 750 psi 1500 psi HTPB" 10 lsodeeyl 10 0.54 0.84

Pelargonate A ls'odecyl 70 10 0.71 0.97

- Pclargonale HTPB" ll lsodeeyl 70 10 NBF**.2 0.71 0.97

Pelargonate Unmodified hydroxy-terminated polyhutadlenc.

" n hutyl ferrocenc. a standard burning-rate promoter.

mark, Emolein from Emery Industries, Inc. Other suit-- able plasticizers include diisooctyl azelate; di-2- ethylhexyl azelate, and dipropylene glycol dipelargonate.

The plasticizers noted above may be used with the copolymers of this invention in amounts from about 5 to about 25 weight percent of the propellant composition. The ammonium perchlorate may vary from about 50 to about 70 weight percent of the propellant composition. The copolymers of this invention may be used in propellant compositions in amounts from about 5 to about 30 weight percent. Aluminum metal from about 5 to about weight percent may be used in the propellant composition containing the copolymers of this invention. v

The copolymers of this invention may be substituted for polybutadiene and the burning rate catalyst employed in a propellant composition since the copolymers contain a catalyst as an integral part thereof. The copolymers of this invention are particularly attractive as a source of catalysis for the propellant composition in order to avoid the problems associatedwith the use of liquid catalysts (e.g. problems, such as, loss by evaporation or migration within the propellant during storage).

We claim: 1 -l. A polymerizable monomer selected from pentaerythritol methacrylate tris (ferrocenoate) and pentaerythritol acrylate tris (ferrocenoate) reacted with butadiene to form a copolymer.

2. The copolymer of claim 1 wherein said butadiene and said selected monomer are reacted in the presence of a suitable initiator contained in a suitable'organic solvent for a predetermined period of time and at a predetermined temperature; said butadiene and said selected monomer being present in a mole ratio of butadiene to monomer from about 40 to l to about 80 to l.

3. The copolymer of claim 2 wherein said selected monomer is pentaerythritol acrylate tris (ferrocenoate); said suitable solvent is toluene; said predetermined period of time is about 72 hours; said predetermined temperature is from about 66C to about 67C; and said suitable initiator is azo-bis-(2-methyl-5- hydroxy-valeronitrile).

4. The copolymer of claim 2 wherein said selected monomer is pentaerythritol methacrylate tris (ferrocenoate); said suitable solvent is toluene; said predetermined period of time is about 72 hours; said predetermined temperature is from about 66C to about 67C; and said suitable initiator is azo-bis-(2-methyl-5- 'hydroxyvaleronitrile 5. The copolymer of claim 4 characterized by a molecular weight in the range from about 3500 to about 4700, OH end groups from about 0.8 to l.2 weight percent, and Fe content from about 3.9 to about 6.9

weight percent.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,857,870 Dated 12/31/7h Inventor(s) Travis E. Stevens et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the Cover Sheet, item should read Assignee:

United States of America as r'espresnted by the Secretary of the Army.

Signed and sealed this 3rd day of June 1975.

(SEAL) Attest:

. C. I-(ARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,857,870 Dated 12/51/7 Inventor(s) Travis E. Stevens et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the Cover Sheet, item should read Assignee:

United States of America as respresnted by the Secretary of the Army.

Signed and sealed this 3rd day of June 1975.

(SEAL) Attest:

. V C. B-TARSTL'XLL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 

1. A POLYMERIZABLE MONOMER SELECTED FROM PENTAERYTHRITOL METHACRYLATE TRIS (FERROCENOATE) AND PENTAERYTHRITOL ACRYLATE TRIS (FERROCENOATE) REACTED WITH BUTADIENE TO FORM A COPOLYMER.
 2. The copolymer of claim 1 wherein said butadiene and said selected monomer are reacted in the presence of a suitable initiator contained in a suitable organic solvent for a predetermined period of time and at a predetermined temperature; said butadiene and said selected monomer being present in a mole ratio of butadiene to monomer from about 40 to 1 to about 80 to
 3. The copolymer of claim 2 wherein said selected monomer is pentaerythritol acrylate tris (ferrocenoate); said suitable solvent is toluene; said predetermined period of time is about 72 hours; said predetermined temperature is from about 66*C to about 67*C; and said suitable initiator is azo-bis-(2-methyl-5-hydroxy-valeronitrile).
 4. The copolymer of claim 2 wherein said selected monomer is pentaerythritol methacrylate tris (ferrocenoate); said suitable solvent is toluene; said predetermined period of time is about 72 hours; said predetermined temperature is from about 66*C to about 67*C; and said suitable initiator is azo-bis-(2-methyl-5-hydroxyvaleronitrile).
 5. The copolymer of claim 4 characterized by a molecular weight in the range from about 3500 to about 4700, OH end groups from about 0.8 to 1.2 weight percent, and Fe content from about 3.9 to about 6.9 weight percent. 